来源:Normally Open (NO) vs Normally Closed (NC): An Overview (electricalterminology.com)
Normally Open (NO) vs Normally Closed (NC): An Overview 常开和常闭概述
2 years ago
There are different contact scheme configurations to solve the various needs of the appliance problems: Normally open contacts (NO), normally closed contacts (NC), and change-over contacts (CO) are the basic configurations. By using these basic contacts, we can construct many configurations to succeed in solving the problems of appliances. I define and compare these contacts for you. After reading you will fully understand their differences.有不同的触点方案配置来解决设备的各种需求：常开触点（NO）、常闭触点（NC）和转换触点（CO）是基本配置。通过使用这些基本触点，我们可以构建许多配置，以成功解决电器问题。我为您定义并比较这些接触。看完之后，你会完全理解他们的不同之处。
What is a Normally Open Contact?什么时常开接触
The contact in relays or switches that is normally open; and closes upon operation is called normally open contact.继电器或开关中常开的触点；并且在操作时闭合被称为常开触点。
It is also called front contact, make contact and form A contact.它也被称为前触点、闭合触点和形成A触点。
Normally open (NO) contact does not conduct electrical energy in its initial position. The force that moves the normally open to the closed position can be a physical action or electromagnetic energization.常开（NO）触点在其初始位置不传导电能。将常开位置移动到关闭位置的力可以是物理动作或电磁激励。
For example;
If you press a normally open pushbutton, the contact of the button changes its position to closed and starts to conduct electricity. Or if you energize the coil of a contactor the magnetic force of the coil will push the main contact and electrons starts to flow from one point to another.如果您按下一个常开按钮，按钮的触点将其位置变为闭合并开始导电。或者，如果你给接触器的线圈通电，线圈的磁力将推动主触点，电子开始从一个点流向另一个点
Some applications of NO contact are pushbuttons, light switches, doorbells, footswitches, NO contactors, and relays.NO触点的一些应用包括按钮、灯开关、门铃、脚踏开关、NO接触器和继电器。
What is a Normally Closed Contact?什么时常闭触点
The contact in relays or switches that is normally closed; and opens upon operation is called normally closed contact.继电器或开关中常闭的触点；并且在操作时打开的触点称为常闭触点。
It is also called back contact, break contact, or form B contact.它也称为反向接触、断开接触或B型接触。
Normally closed contact (NC) is the exact opposite of normally open contact by function. Normally closed contact conducts electrical energy in its initial position. The force that moves normally closed to the open position can be a physical action or electromagnetic de-energization.常闭触点（NC）的功能与常开触点完全相反。常闭触点在其初始位置传导电能。通常关闭到打开位置的力可以是物理动作或电磁断电。
Some applications of NC contact are emergency stop buttons, NC contactors, and relays.NC触点的一些应用是紧急停止按钮、NC接触器和继电器。
What is a Changeover Contact?什么是转换触点？
A combination of normally closed and normally open contact is referred to as a changeover contact. 常闭触点和常开触点的组合称为转换触点。
The roots of the normally open and normally closed contacts are connected. Therefore, the changeover contact (CO) has three connections. It is also called switch-over contact, transfer contact, or Form C contact.连接常开触点和常闭触点的根部。因此，转换触点（CO）有三个连接。它也称为转换触点、转换触点或C型触点。
Some applications of CO contact are control relays and PLCs.CO触点的一些应用是控制继电器和PLC。
Comparison of NO, NC, and CO contactsNO、NC和CO触点的比较
